Petrol–electric transmission or gasoline–electric transmission or gas–electric transmission is a transmission system for vehicles powered by petrol engines. Petrol–electric transmission was used for a variety of applications in road, rail, and marine transport, in the early 20th century. After World War I, it was largely superseded by diesel-electric transmission, a similar transmission system used for diesel engines; but petrol-electric has become popular again in modern hybrid electric vehicles.

A diesel–electric transmission, or diesel–electric powertrain, is a transmission system for vehicles powered by diesel engines in road, rail, and marine transport. Diesel–electric transmission is based on petrol–electric transmission, a transmission system used for petrol engines.